0000000000081730
AUTHOR
Francesca Rita Pomilla
Comparison between catalytic and photocatalytic activity in gas-solid regime of semiconductor oxides and carbon nanotubes supported Keggin heteropolyacid.
Catalytic and photocatalytic 2-propanol dehydration was carried out by using a supported Keggin heteropolyacid H3PW12O40 (PW12). Binary materials were prepared by impregnation and/or solvothermal treatment by using commercial supports: SiO2 (Mallinckrodt), TiO2 (Evonik P25) and multiwall carbon nanotubes (Sunnano) or home solvothermically prepared SiO2 and TiO2. All the materials have been characterized by X-ray diffraction (XRD), scanning electron microscopy observations (SEM) coupled with EDX microanalysis, specific surface area measurements, diffuse reflectance spectroscopy (DRS), FTIR and Raman spectroscopy. (Photo)catalytic 2-propanol dehydration was studied in gas-solid regime by usin…
ZrO2 Based materials as photocatalysts for 2-propanol oxidation by using UV and solar light irradiation and tests for CO2 reduction
Abstract Bare ZrO2, Ce doped ZrO2 and Er doped ZrO2 samples have been prepared by a hydrothermal process and have been used as photocatalysts for 2-propanol oxidation reaction in gas solid regime. Moreover, some preliminary tests have been carried out for CO2 reduction. The samples were physico-chemically characterized and both bare and doped ZrO2 based materials resulted active for oxidation and reduction reactions by using UV and solar irradiation. The reactivity results have been correlated with the compositional, structural and morphological features of the photocatalysts.
Role of the support on the activity of H3PW12O40 supported on SiO2 or TiO2 in Catalytic and Photocatalytic propene hydration: An EPR Study
Catalytic and catalytic photo-assisted hydration of propene to 2-propanol in gas-solid regime at atmospheric pressure and 85°C were carried out by using the Keggin heteropolyacid (HPA) H3PW12O40 (PW12) supported on home prepared SiO2, WO3, TiO2 or N-doped TiO2. The HPA played the key role both in catalytic and photocatalytic reactions; however, the support strongly influenced the binary material performance. The contemporary presence of heat and UV light improved the activity of the (photo)catalysts. EPR (Electron Paramagnetic Resonance) has been used to understand the intimate mechanism underlying the photoactivity of the supported heteropolyacid and the role played by the support.
CO2 to Liquid Fuels: Photocatalytic Conversion in a Continuous Membrane Reactor
The photocatalytic reduction of CO, into value-added chemicals using sunlight is a promising approach to promote energy-bearing products, mitigating the adverse effects of anthropogenic CO2 emissions. In this work, exfoliated C3N4 was incorporated into Nafion matrix and used in a continuous photocatalytic reactor for converting CO2 into liquid fuels. Comprehensive structural and morphological diffuse reflectance spectroscopy (DRS), FT-IR, ATR-IR, and SEM measurements were performed for C3N4-loaded Nafion membrane and then compared with those of a Nafion membrane without any catalyst. The synergic effect of C3N4 organic catalyst embedded in a Nafion dense matrix and a continuous operating mo…
Role of the support and pseudo-liquid phase in the Phosphotungstic Heteropolyacid (photo)catalytic activity
Catalytic and photocatalytic tests for propene hydration to 2-propanol were successfully carried out by using binary materials obtained by supporting a Keggin or Wells-Dawson heteropolyacids via impregnation method to commercial SiO2 or TiO2. (Photo)catalytic hydration was studied in gas-solid regime by using a continuous (photo)reactor working at atmospheric pressure and 80 °C. The alcohol was the main product. The acidity of the cluster accounts for the catalytic role, whereas both the acidity of the cluster and the oxidant ability were responsible for the increase of the reaction rate of the photo-assisted catalytic reaction. Moreover, the presence of a photoactive semiconductor support …
Photocatalytic conversion of glucose in aqueous suspensions of heteropolyacid-TiO2 composites.
Photocatalytic conversion of glucose was carried out in aqueous suspensions in the presence of dfifferent commercial and home prepared TiO2 samples functionalized with a commercial heteropolyacid. Different reaction extents and distribution of intermediate oxidation products were observed depending on the photocatalyst.
Synthetic Green Chemistry through Heterogeneous Photocatalysis
This contribution deals with a short review of some application of TiO2 to green organic synthesis. In particular to selective oxidation of aromatic alcohols under mild conditions.
Enhanced (photo)catalytic activity of Wells-Dawson (H6P2W18O62) in comparison to Keggin (H3PW12O40) heteropolyacids for 2-propanol dehydration in gas-solid regime
Abstract Catalytic and photocatalytic 2-propanol dehydration to propene at atmospheric pressure and a temperature range of 60–120 °C were carried out in gas-solid regime by using bare and supported Keggin H 3 PW 12 O 40 (PW 12 ) and Wells-Dawson H 6 P 2 W 18 O 62 (P 2 W 18 ) heteropolyacids (HPAs). Binary materials were prepared by impregnation of the HPAs on commercial SiO 2 and TiO 2 . The Wells-Dawson was in any case more active than the Keggin heteropolyacid and the differences were enhanced when the supported samples were used. In particular, Wells-Dawson HPA supported on TiO 2 and under irradiation showed the highest activity. The HPA species played the key role both in the catalytic …
Properties of titanium dioxide
"Properties of titanium dioxide" presents a survey of the main physicochemical properties of TiO2 upon which rely all of the applications of this material. Structures and morphologies of titanium dioxide have been taken into account, also in correlation with thermodynamic properties. Bulk and surface defectivity has been described in detail, because of its relevant consequences in terms of catalytic activity. The basic mechanisms of interaction between photons and TiO2 have been discussed on the basis of the optoelectronic features of the semiconductor. Finally, electrical, mechanical, and rheological properties of TiO2 have been presented.
CO2 reduction by C3N4-TiO2 Nafion photocatalytic membrane reactor as a promising environmental pathway to solar fuels
Abstract We investigated CO2 photocatalytic reduction coupling, for the first time in literature, the assets offered by the continuous operating mode using C3N4-TiO2 photo-catalyst embedded in a dense Nafion matrix. The reactor performance was analyzed under UV–vis light in terms of productivity, selectivity and converted carbon. Reaction pressure was specifically investigated for its effect as a “driver” in determining reactor performance, modulating products removal from the reaction volume. In addition, the membrane reactor performance was explored as a function of H2O/CO2 feed molar ratio and contact time. The higher feed pressure (5 bar) led to a lesser MeOH production and a greater am…
Confronto tra attività catalitica e fotocatalitica dell’eteropoliacido di Keggin H3PW12O40 supportato su ossidi o su nanotubi di carbonio
Catalytic and catalytic photo-assisted dehydration of 2-propanol to form propene in gas-solid regime at atmospheric pressure and 80°C was carried out by using a Keggin heteropolyacid H3PW12O40 (PW12) supported on different oxides. Binary materials have been prepared by impregnation of PW12 on different commercial and home prepared supports (TiO2, SiO2 or carbon nanotubes). The supported Keggin PW12 species played a key role both for the catalytic and the photo-assisted catalytic reactions, due to their strong acidity and ability to form strong oxidant species under UV irradiation, respectively. The contemporary presence of heat and UV light improved the activity of almost all POM supported …
An Investigation into the Stability of Graphitic C 3 N 4 as a Photocatalyst for CO 2 Reduction
The increasing CO 2 concentration in the atmosphere exerts a significant influence on global warming and climate change. The capture and utilization of CO 2 by conversion to useful products is an area of active research. In this work, the photodriven reduction of CO 2 was investigated using graphitic carbon nitride (g-C 3 N 4 ) as a potential photocatalyst. The photocatalytic reduction of CO 2 was investigated with g-C 3 N 4 powder immobilized on a glass support in a batch gas-phase photoreactor. The experiments were carried out under UV-vis irradiation at 70 °C and an initial pressure of 2.5 bar. The only gas-phase product detected during the irradiation of the g-C 3 N 4 in the presence of…
Photoelectrochemical and EPR features of polymeric C 3 N 4 and O-modified C 3 N 4 employed for selective photocatalytic oxidation of alcohols to aldehydes
Four different C 3 N 4 specimens have been prepared, a bulk one (MCN), a thermally etched (MCN-TE), a solid prepared by hydrothermally treating MCN with H 2 O 2 (MCN-H 2 O 2 ) and a polymeric carbon nitride-hydrogen peroxide adduct (MCN-TE-H 2 O 2 ). The principal aim of this work was to correlate the capability of the prepared material to generate reactive oxygen species (ROS), under irradiation, with their photocatalytic activities in terms of conversion and selectivity for partial oxidation reactions. Photoelectrochemical studies revealed that MCN-TE represented the best material in terms of photoconductivity, whereas MCN-H 2 O 2 was defective and evidenced a poor mobility of carriers. E…
Comparison of activity in the 2-propanol dehydration of supported heteropolyacid (photo)catalysts at the gas-solid interface
Catalytic and photocatalytic tests for 2-propanol dehydration to propene were successfully carried out by using binary materials obtained by supporting a Keggin heteropolyacid H3PW12O40 (PW12) via impregnation method and/or solvothermal treatment. The supports used were commercial SiO2 (Mallinckrodt), TiO2 (Evonik P25) and multiwall carbon nanotubes (Sunnano) or home solvothermically prepared SiO2 and TiO2. (Photo)catalytic 2-propanol dehydration was studied in gas-solid regime by using a continuous (photo)reactor working at atmospheric pressure and 80 °C. the reaction was also studied by performing FTIR spectra of the gas-phase over the HPA-support composites, where the 2-propanol had been…
Heteropolyacids supported on boron nitride and carbon nitride for catalytic and catalytic photo-assisted alcohol dehydration
Keggin H3PW12O40 (PW12) and Wells-Dawson H6P2W18O60 (P2W18) heteropolyacids (HPAs) are photo(catalysts) for various acid-promoted and redox catalytic reactions. Their activity increases if they are deposited on certain supports as metal oxides or carbon materials. Although the surface area and acid-base interactions of the HPAs with supports are considered as key factors for the performance of the binary material, the role of the local structure changes in the HPAs upon their immobilization on solids must be also of primary importance, directly affecting both acidity and photoredox properties. Here, the (photo)catalytic performance of Keggin and Wells-Dawson heteropolytungstates supported o…
Keggin heteropolyacid supported on BN and C3N4: Comparison between catalytic and photocatalytic alcohol dehydration
The Keggin heteropolyacid (HPA), H3PW12O40 (PW12) has been supported on commercial boron nitride (BN) and two types of home prepared carbon nitride (C3N4). The supported PW12 was used in the gas-solid (photo)catalytic 2-propanol dehydration reaction to give propene at atmospheric pressure and temperatures in the range 70–120 °C and resulted more active than the pristine PW12. Reaction rate increased by increasing the temperature. Noticeably, the propene formation rate was higher by irradiating the catalytic system. The PW12/BN material resulted more active than PW12/C3N4. The acidity of the HPA cluster accounts for the catalytic role, whereas both the acidity and the redox properties of the…
Improved (photo)catalytic propene hydration in a gas/solid system by using heteropolyacid/oxide composites: Electron paramagnetic resonance, acidity, and role of water
Binary materials composed of the oxides SiO2, TiO2 and N-doped TiO2 and the Keggin heteropolyacid (PW12) were prepared and physicochemically characterized. They were used as catalysts and photocatalysts for the hydration of propene to 2-propanol. The characterization of the samples, particularly the electron paramagnetic resonance (EPR) spectroscopy results and the acidity properties, were useful to explain the key role played by the PW12 in the composite materials in the thermal and photoassisted catalytic processes. The simultaneous pres-ence of heat and UV light improved the activity of PW12 in the thermal process, and the binary materials showed better (photo)catalytic activities than t…
Keggin and Wells-Dawson supported heteropolyacids as heterogeneous (photo)catalysts for gas-solid 2-propanol dehydration
Catalytic and photocatalytic tests for 2-propanol dehydration to propene were successfully carried out by using binary materials obtained by supporting a Keggin or Wells-Dawson heteropolyacids via impregnation method to commercial SiO2 or TiO2. (Photo)catalytic 2-propanol dehydration was studied in gas-solid regime by using a continuous (photo)reactor working at atmospheric pressure and 80 °C. Propene and diisopropyl ether were the main reaction products. For the continuous photo-assisted runs the reactor was also illuminated with UV light. The heteropolyacid species played a key role both for the catalytic and the photo-assisted catalytic reactions; indicating that the acidity of the clust…
Reazione catalitica e fotocatalitica di disidratazione in fase gas-solido del 2-propanolo in presenza di eteropoliacidi "Keggin" e "Wells-Dawson" supportati
La disidratazione catalitica e fotocatalitica di 2-propanol a propilene è stata effettuata usando eteropoliacidi di Keggin H3PW12O40 (PW12) e Wells-Dawson H6P2W18O60 (P2W18). Sono stati utilizzati sia supportani che non. Materiali binari sono stati preparati per l'impregnazione degli eteropoliacidi su supporti commerciali: SiO2 (Aldrich) e TiO2 (Evonik P25). I materiali sono stati caratterizzati e la loro (foto) attività catalitica rispetto alla disidratazione 2-propanol evaluata in regime gas-solido utilizzando un reattore continuo a pressione atmosferica e un range di temperatura fra 60 e 120 ° C. Inoltre, per gli esperimenti fotoassititi il reattore è stato illuminato da un LED UV. Impor…
Photocatalytic conversion of glucose in aqueous suspensions of heteropolyacid-TiO2 composites.
Commercial and home prepared TiO2 samples were functionalized with a commercial Keggin heteropolyacid (HPA) H 3PW12O 40 (PW12) or with a hydrothermally home prepared K 7PW11O 39 salt (PW11). All the materials were characterized by specific surface area measurements (BET), XRD analyses, Raman, DRS along with SEM observations and they have been used for glucose photocatalytic conversion in an aqueous suspension. Different reaction extents and distribution of intermediate oxidation products were observed depending on the photocatalyst. Gluconic acid, arabinose, erythrose and formic acid were observed as oxidation products when bare TiO2 or HPA/TiO2 composite materials were used. Glucose isomer…
Catalytic Dehydration of Fructose to 5-Hydroxymethylfurfural in Aqueous Medium over Nb2O5-Based Catalysts
The catalytic dehydration of fructose to 5-hydroxymethylfurfural (HMF) in water was performed in the presence of pristine Nb2O5 and composites containing Nb and Ti, Ce or Zr oxides. In all experiments, fructose was converted to HMF using water as the solvent. The catalysts were characterized by powder X-ray diffraction, scanning electron microscopy, N2 physical adsorption, infrared and Raman spectroscopy and temperature-programmed desorption of NH3. Experimental parameters such as fructose initial concentration, volume of the reacting suspension, operation temperature, reaction time and amount of catalyst were tuned in order to optimize the catalytic reaction process. The highest selectivit…
Supported H3PW12O40 for 2-propanol (photo-assisted) catalytic dehydration in gas-solid regime: The role of the support and of the pseudo-liquid phase in the (photo)activity
Abstract Catalytic and photocatalytic 2-propanol dehydration was carried out by using a supported Keggin heteropolyacid H3PW12O40 (PW12). Binary materials were prepared by impregnation and/or solvothermal treatment by using commercial supports: SiO2 (Mallinckrodt), TiO2 (Evonik P25) and multiwall carbon nanotubes (Sunnano) or home solvothermically prepared SiO2 and TiO2. All the materials have been characterized by X-ray diffraction (XRD), scanning electron microscopy observations (SEM) coupled with EDX microanalysis, specific surface area measurements, diffuse reflectance spectroscopy (DRS), FTIR and Raman spectroscopy. (Photo)catalytic 2-propanol dehydration was studied in gas-solid regim…